Fire detection is an important concern for a variety of different commercial and industrial areas. Fire detection systems are available to sense various attributes of a fire and to warn when a fire is detected. For example, smoke detectors include sensors adapted to sense smoke associated with a fire and to trigger an alarm when a selected level of smoke is detected. Other detectors sense other attributes associated with a fire.
Ultraviolet (UV) light emitted from flames of a particular fire is detected by a flame detector system's UV sensor. When a selected amount of UV light is detected, the flame detector system triggers an alarm.
To ensure their reliable performance and functionality, UV flame detectors are tested periodically. One method of testing involves using a test lamp that emits a broad spectrum of UV light at wavelengths of about 180 nanometers (“nm”) to 350 nm. The light is directed towards the UV sensor of the flame detector. If the UV sensor does not detect the light from the tests lamp within an expected range, the detector goes into fault. The UV emitters are often encased within the detectors for simplicity, and convenience.
An example of a type of UV emitter used for optical integrity testing is a Neon glow lamp. This Neon glow lamp is a small device made from glass that is transparent and configured to emit UV light at wavelengths in the range of approximately 200 nm to 350 nm. This Neon glow lamp encases a rarified atmosphere of Neon, Hydrogen, and Argo, as further described in detail in the description of the drawings.
When positioned inside the casing of the detectors, the UV emitters are subject to a phenomenon commonly known as “dark effect.” In particular, when Neon Glow UV emitters are stored in the dark for extended periods of time, and without operation, the Neon Glow UV emitters require a higher strike voltage of approximately 240 to approximately 1000 volts, in order to spark or light up and operate again. Additionally, the Neon Glow UV emitters require longer strike duration (i.e. the time it takes for the Neon Glow UV emitter to light up and operate). Typically, strike durations can exceed approximately 10 milliseconds for any subsequent operation after long periods of storage in the dark. This dark effect results in delayed starting and erratic operation of the Neon Glow UV emitter.
The most commonly employed method of overcoming the dark effect in Neon Glow UV emitters is the addition of radioactive Krypton 85 gas (Kr85) within the emitter at very small amounts. The use of Kr85 to neutralize the dark effect may substantially increase the material costs and/or manufacturing costs. Additionally, the use of Kr85 imposes severe regulatory hurdles. Changes in international regulations surrounding the use and shipment of radioactive materials, such as Kr85, have made it difficult to ship flame detectors with Neon Glow UV emitters containing radioactive materials. Additionally, the effectiveness of the use of Kr85 decreases during the life of the Neon Glow UV emitter, thereby rendering the operation of the flame detector erratic and terminating its useful life.
An effective and reliable Neon Glow UV emitter that operates without a need for radioactive materials would dramatically improve the cost, simplicity, and ease of use of flame detectors. Accordingly, there exists a need for a flame detector using a Neon Glow UV emitter that does not contain radioactive materials.